Tamper evident lid welded to a container

ABSTRACT

A tamper-evident plastic lid is welded to a plastic container at a welded portion and a detachable, replaceable lid portion is formed by tearing a frangible portion on the lid&#39;s skirt thereby leaving a torn tamper-evident, welded lid portion fixed to the container rim. The illustrated lid is a plug-fit lid which has a plug-shaped portion comprising a depressed central panel and an encircling, upstanding wall that engages an inner side of the container rim wall to retain the separated lid portion when it is replaced on the container. An energy director preferably in the form of an encircling bead on the lid initiates the softening of the plastic of the bead for welding with the plastic of the container rim. The preferred frangible portion is a reduced cross-sectional thickness web in a horizontally and radially extending skirt wall on the lid skirt overlying a horizontally and radially extending rim wall on the container rim. The frangible portion may be located radially inwardly of the welded portion. A pull tab may be provided on the replaceable lid portion to assist in initiating the fracturing of the thin frangible web. A pry slot may also be provided to aid in locating where and how to separate the replaceable lid portion from the welded portion which is permanently attached to the container.

FIELD OF THE INVENTION

This invention relates to a tamper-evident plastic lid and to the combination of the lid welded to a rim of a plastic container.

BACKGROUND OF THE INVENTION

The present invention is directed to a one-piece plastic lid which is often applied to a plastic container to provide a tamper-evident replaceable lid such that when it is removed it is apparent to the user that the lid has been tampered with. The lid is replaceable in the sense that after using some of the contents or accessing the contents, the lid may be repositioned back onto container in a retained or a generally sealed position to protect the contents against contamination or the like.

Lids of this general type are usually lightweight, inexpensive and stackable such that they can be stacked in lid applying machines which feed the lids and automatically apply them to filled containers.

The present invention will be described in conjunction with a preferred and illustrated use, which is that of a lid of the so-called recessed central plug kind which fits into the container and is replaceable to have a friction interfit with the container after the lid has been initially removed from the container. The illustrated container is that commonly used in dairy applications for dairy products such as cottage cheese and involves a lightweight plastic tub-like container with an annular rim into which is fitted the plug-fit lid. To provide a tamper-evident feature to this plug-fit lid and container, a thin, clear discrete band of clear plastic is wrapped about the container rim and lid skirt and this thin, frangible band must be broken and removed before the lid can be removed from the container. The attaching of this clear band and the cost of this clear band are desired to be eliminated. Thus, there is a need for a new, improved lid and container construction.

SUMMARY OF THE INVENTION

In accordance with the preferred embodiment, there is provided a new and improved tamper-evident lid for attachment to a plastic container which is welded to the plastic container to provide a permanent interconnection with the container to prevent tampering with the container contents. A frangible portion is provided on the lid which can be broken to allow detachment of a replaceable lid portion while leaving a welded portion of the lid welded to the skirt of the container which shows that the lid has been removed.

In accordance with the preferred embodiment, there is provided a plug-type lid which has a central, recessed panel and an upstanding skirt with a horizontally extending rim portion which is welded to the rim of the container. The frangible portion on the skirt is located radially inward of the welded portion and is fractured to allow removal of the replaceable lid from the outer skirt portion of the lid which remains permanently attached to the rim of the container. The plug lid may be fitted and pressed back in place, that is replaced to cover the contents after they have been accessed and it is desired to replace the lid. This plug lid portion has a friction interfit with the container rim to retain the lid portion on the container. The frangible portion is preferably a very thin web of reduced cross-sectional thickness which when is subjected to a pulling force fractures and disconnects the detachable lid from the welded lid portion which remains on the container rim.

A pull tab may be connected to the detachable lid portion to assist in starting and in fracturing the frangible portion. The preferred welding is achieved by the use of a energy director such as a depending bead on the underside of the skirt which is welded to the horizontal portion of the rim of the container. Also, a pry slot may be provided on the lid to locate and to indicate where and how the lid portion is detached from the welded portion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a lid and a container and constructed in accordance with one embodiment of the invention;

FIG. 2 is a plan view of the lid of FIG. 3;

FIG. 3 is another perspective view of another embodiment of a lid and a container;

FIG. 4 is an enlarged cross-sectional view of a lid skirt having an energy director and a frangible portion;

FIG. 5 is a cross-sectional view taken along the line 5-5 of FIG. 2;

FIG. 6 is an enlarged cross-sectional view of a skirt portion of the lid;

FIG. 7 is an enlarged cross-sectional view of the lid showing an internal rib in the lid;

FIG. 8 is a cross-sectional view showing the lid welded to a rim of the container; and

FIG. 9 is a side elevational view of a container used with a weldable lid.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

As shown in the drawings for purposes of illustration, a container and lid assembly 10 is illustrated as comprising a container 11 of plastic material and a lid 12 of plastic such as polypropylene. The container may also be made of a suitable plastic. Both the lid and the container may be made of various plastic materials, although polypropylene is preferably selected for the lid because it is lightweight and inexpensive and has good properties when subjected to extreme cold as may be the case with various dairy products.

The lid 12 herein is an injection molded plastic lid that is welded to an injection molded plastic container 11. To provide a lightweight and low cost injection molded lid and container, they are each preferably made of polypropylene plastic. It is to be understood that the lid and/or container may be made by a thermoforming technique rather than an injection molding technique and still fall within the purview of this invention. Also, the present invention is not limited to use of polypropylene as the plastic for either the lid and the container as they made be made of polyethylene or other plastics and still fall within the purview of this invention.

The illustrated lid 12 is of the plug type in that it has a depending recessed, plug portion 14 which has an outer, encircling upper skirt 16 integrally joined at its lower end to a flat, wide circular central panel portion 18 which is located at the center of the lid. The skirt 16 is joined to the central panel 18 by an annular, vertical sidewall 20. Although the invention is described herein as a tamper-evident plug-fit lid that is welded to the container, it is to be understood that the invention is not limited to a plug kind of lid. Manifestly, the lid could have a replaceable portion that is not in the shape of a plug and falls within the purview of the claims defining this invention.

The illustrated container 11, as shown in FIGS. 1 and 8, has an encircling radially outwardly extending rim portion 22 projecting outwardly from the top of an inclined sidewall 24 which is integrally joined at its lower end to a bottom wall 26 for the container. The illustrated container is also injected molded of a plastic material. The rim portion 22 has a flat, annular horizontally disposed rim wall 22 a which extends radially outward of the inclined sidewall and terminates in a depending flange 22 b which fits within a depending flange 34 on the skirt of the lid.

In accordance with the illustrated embodiment, the lid is sealed and is attached to the rim of the container by a weldable portion 28 which is permanently welded to the container rim 22 as shown in FIG. 8 substantially all the way around the lid and the container to make a sealed connection therewith. The preferred welded portion includes an energy director 30 (FIGS. 4 and 6) in the form of an encircling annular, bead 32 of plastic depending from a lower surface of an annular, horizontal skirt wall 33 on the lid, as best seen in FIG. 6. The bead 32 has a pointed lower tip 35 which concentrates the ultrasonic welding energy at the tip to quickly raise its temperature of the pointed bead to a melting temperature to aid in initiating the plastic flow of the bead into softened plastic being melted on the encircling, horizontal flange 34 of the container rim 22.

When opening the container to access the contents therein, the lid is lifted and pulled upwardly to fracture a frangible portion 40 which is preferably in the form of a thin web 42 (FIG. 4) having a reduced cross-section from the remainder of the skirt 16 of the lid. By way of example only, the horizontal extending flange of the lid carrying the lid may be about 0.018 inch thick with the bead about 0.025 inch thick and with the frangible groove portion 40 being several thousandths of an inch less than 0.018 inch in cross-sectional thickness of the skirt wall 33. The welded portion 28 is radially outward of the frangible groove 42 in the skirt wall 33 so that it remains welded to the rim of a container as the frangible web is broken. This leaves the central detachable, and replaceable lid portion 50 having an annular outer edge having once been a portion of the groove 42 at the location of the thin web in the skirt wall 33. Manifestly, the breaking and tearing of the frangible web provides a tamper-evident feature to the user so that it is evident when the lid has been removed and the contents of the container accessed by someone. After accessing the contents, the user may reapply the lid merely by setting it back with the central plug having its vertical sidewall 20; and then pushing the lid down into frictional engagement with the vertical sidewall 24 of the container. Herein, the lid vertical sidewall 20 is slightly inclined or tapered by about 0.005 inch from its upper end at the lid skirt to a smaller diameter at its lower end 20 b which is joined to a reduced diameter section 20 a which is integrally joined to the central panel 18.

In the embodiment illustrated in FIG. 1, the substantially annular channel or fracturable portion 40 and the thin web 42 are formed to extend and to be located downwardly within the skirt wall 33 and then are attached to a separate pull tab 55 as best seen in FIG. 1. By grasping the pull tab and pulling it upward, the frangible web will be fractured and torn continually along the substantially annular thin web 42 so that the replaceable lid portion, after it is detached from the welded portion on the container, has an integral pull portion 55 thereon.

In the embodiment shown in FIGS. 2 and 3, the pry slot 62 has been formed in the lid skirt 16. Thereby making it more obvious to the user as to where to start to separate the lid portion from the container. As shown in FIGS. 2 and 3, the pry slot 62 is formed at the skirt and at the pull strip 55 which can be lifted by placing a screwdriver or finger or some other implement into the pry slot and exerting an upward force until the thin channel frangible portion 40 tears around the perimeter of the lid. Once the tear has been completed, the skirt outer annular portion outward of the frangible groove would be retained and attached to the container while the replaceable central panel lid would be detached. Later the plug central panel lid portion can be reapplied by inserting it back into place and pushing down on it.

The illustrated lids are stacked and nested, one within another, with a corner 20 e (FIG. 6) at the juncture of the lid sidewall 20 and the central panel resting on stacking ribs 70 formed at spaced locations on the lid sidewall 20. In order to prevent a vacuum from forming between adjacent stacked lids as interferes with feeding automatically, the ribs 70 also serve as an internal venting facilities. The preferred venting and stacking ribs 70 are preferably located at 45° spacing about the circumference of the skirt wall 20 and projected radially inwardly about the interior of the lid sidewall 20, as shown in FIG. 7. The illustrated ribs extend downwardly to the lid central panel 18 and extending upwardly above a radius shoulder 20 c as shown in FIG. 7 between the upper portion 20 b of the lid sidewall 20 and the lower portion 20 a of the lid sidewall 20 as shown in FIGS. 5 and 7. With the lids nested for feeding by an automatic lid applying machine, the smaller diameter central panel 18 of an upper lid is seated on a top edge 76 of the spaced ribs 70 in a nested position. The top edge 76 of the venting facility rib 70 is located at a height such that it seats a nested lid thereabove with its lower outer edge 78 on its depending skirt flange 66 spaced from the horizontal skirt wall 33 of a lid therebelow to provide a slot or space to allow the insertion of a finger of a lid removing and lid applying equipment for such lids. It is most desirable and necessary that the lid be machine useable with conventional existing package and machinery.

Although the energy direction has been shown and described as being on the lid, it is to be understood that the energy director could be on the container rim and still fall within the purview of the claims of the invention. The frangible portion is described and illustrated as a thin web in the skirt wall, but is to be understood that a scored portion or other weakened portion on the lid may be the frangible portion and that the frangible portion could be repositioned to a location other than that on the horizontally extending skirt wall as illustrated in the embodiments herein described.

From the foregoing, it will be seen that there has been provided a new and improved lid and container which have a welded portion retained while the reapplied, tamper-evident lid portion is free to be reapplied after the contents of the container accessed to protect the container contents until it is desired to access again the contents. 

1. A tamper-evident lid for attachment to a rim of a container, the lid comprising: a lid body made of plastic; a central separable lid portion on the plastic, lid body; a skirt on the plastic lid body for permanent attachment to the container; a weldable portion on the skirt for being welded to the container; a detachable, replaceable lid portion on the lid body for detachment from the skirt of the lid and for replacement on the container to cover container after the initial removal of the lid portion from the container; and a frangible portion on the lid body between the weldable portion and the detachable lid portion for fracturing to leave the weldable portion welded to the container and to allow removal of the detachable, replaceable lid portion from the container.
 2. A tamper-evident lid in accordance with claim 1 wherein the detachable, replaceable lid portion comprises: a recessed central plug having a depressed central panel and an encircling, upstanding sidewall connected to the central panel.
 3. A tamper-evident lid in accordance with claim 2 comprising: a pull tab connected to the central plug for pulling to fracture the frangible portion and to leave the weldable portion attached to the container rim and to allow lifting of the lid portion from the container.
 4. A tamper-evident lid in accordance with claim 1 wherein the weldable portion comprises: an energy director in the form of a depending bead on the underside of the skirt.
 5. A tamper-evident lid in accordance with claim 1 comprising: a pry slot associated with the frangible portion for initiating removal of the detachable, replaceable lid portion.
 6. A tamper-evident lid in accordance with claim 1 wherein the frangible portion comprises a groove forming a reduced cross-section in the skirt for fracturing.
 7. A tamper-evident lid in accordance with claim 1 wherein the lid is made of injection molded plastic.
 8. A lid in accordance with claim 1 wherein the tamper-evident lid is thermoformed.
 9. A tamper-evident lid for being welded to a rim wall on a rim of a container, the lid comprising: a lid body made of plastic; a central panel on the lid body to cover the contents of the container; a skirt on the lid body joined to the central panel and for attachment to the rim of the container; a substantially horizontally and radially extending skirt wall on the skirt for extending over the top of the container's rim wall; a frangible portion on the skirt wall for fracturing to form a replaceable and detachable lid portion that includes the central panel to cover the container contents when the lid is replaced; and a weldable portion on the skirt wall located radially outwardly of the frangible portion to be welded to the container rim wall and to remain welded thereto when the frangible portion is fractured and the replaceable lid portion is detached and removed from the container.
 10. A lid in accordance with claim 9 wherein the weldable portion comprises: an encircling bead formed on the underside of the horizontally and radially extending skirt wall.
 11. A lid in accordance with claim 10 wherein the frangible portion comprises: an annular web of reduced cross-sectional thickness in the horizontally and radially extending skirt wall.
 12. A lid in accordance with claim 11 wherein the lid is a plug-fit lid having a depressed central panel joined to a higher skirt on the lid.
 13. A lid in accordance with claim 9 wherein the tamper-evident lid is made by thermoforming.
 14. A container and tamper-evident lid comprising: a plastic container having an outer and encircling rim portion surrounding an upper opening at the top of the container; a lid body having a skirt for welding to the rim of the plastic container; an encircling horizontal wall on the lid shirt overlying the container rim portion; a welded portion connecting the horizontal wall to the container rim; a frangible portion on the lid body for fracturing to provide a central replaceable lid portion with a portion of the skirt remaining welded to the container rim; and portions interconnecting on the replaceable lid portion and the container to retain the lid portion on the container upon replacement of the lid on the container.
 15. A container and lid in accordance with claim 14 wherein the frangible portion comprises a reduced, cross-sectional web in the lid skirt for tearing.
 16. A container and lid in accordance with claim 14 comprising: an energy director on the skirt for welding to the container rim to form the welded portion between the lid and container.
 17. A container and lid in accordance with claim 14 wherein the replaceable lid comprises: a depressed central panel; an upstanding encircling wall connected to the depressed central panel; and a horizontal flange connected to an upper end of the encircling wall and for overlying the container rim.
 18. A container and lid in accordance with claim 17 wherein the lid can be reapplied by inserting it back into the container opening and pushing down on the lid.
 19. A container and lid in accordance with claim 18 comprising: a pry slot opening in the container rim to allow prying of the replaceable lid from the container.
 20. A container and tamper-evident lid comprising: a plastic container having an outer and encircling rim portion surrounding an upper opening at the top of the container; a lid body having a skirt for welding to the rim of the plastic container; a frangible portion on the lid body for fracturing to provide a central replaceable lid portion with a portion of the skirt remaining welded to the container rim; a horizontally and radially extending rim wall on the container for being welded to the lid skirt; a horizontally and radially extending skirt wall disposed above the container rim wall; and a welded portion joining the respective horizontally and radially extending rim wall and skirt wall at a location radially outwardly of the frangible portion.
 21. A container and lid in accordance with claim 20 wherein the frangible portion comprises: a weakened, substantially annular area in the horizontally and radially extending skirt wall.
 22. A container and lid in accordance with claim 20 comprising: an energy director on the horizontally and radially extending skirt wall for initially softening and welding to the container rim wall.
 23. A container lid in accordance with claim 20 wherein the welded portion is formed by ultrasonic welding using the energy director. 